Cognitive Neuroscience

1. Cognitive Neuroscience

2. What are we doing with our brains right now? • Feeling your chair • Squirming (moving) • Watching • Listening • Remembering • Paying attention • Sleeping • Feeling anxious • Feeling hungry • What happens when you ask a question?

3. The Brain • Approx 3lbs • 1 trillion cells • 100 billion neurons • ½ of neurons are in cerebellum • Each neuron has 5000 – 10,000 synapses • Males and females differ, but only slightly • Neurons transmit signals at speed of about 2 m/s • There are more possible connections in your brain than there are atoms in the universe

4. Cognitive Neurosccience • The cell • Cortex • Mid-Brain • Hindbrain

5. Cell Structure: From an Information Processing View Dendrites receive signals. Signals travel along the Soma or Cell Body and Summate at the Axon Hillock The signal must be above a Threshold for the signal to travel down the Axon

6. Cell Structure: From an Information Processing View Dendrites • Receive in Modulate signals Omnidirectionally • They are graded potentials – they decay as they travel Soma • Where the signals are summed • The amplitude and the timing (concurrence) are important • The signal strength must be greater than the resistance at the axon hillock • The threshold can shift • The soma has a baseline • Baseline indicates all is normal • Indicates cell is alive • Firing is not perfect, Noise: can fire for no reason, or not fire when it “should”

12. Cell Structure: From an Information Processing View Axons • Transmit signals in one direction and are ballistic (all or nothing) • Have myelin sheaths which sustain the signal strengths (do not decay) • Their axon buttons or knobs release neurotransmitters

13. Functional classification Afferent or sensory neuron: conduct impulses from the sensory organs to the central nervous system (brain and spinal cord) Efferent or motor neuron: conduct impulses from the central nervous system to the effector organs (such as muscles and glands) are called motor (or efferent) neurons Interneurons(also known as connector neurons or association neurons): connect sensory neurons to motor neurons.

14. Quizz The dendrite is part of the neuron which • Is covered in myelin sheath • Propagates signals in one direction only • Receives modulated signals • Releases neurotransmitters

15. Functional classification • The glial cells • maintain the ionic environment • modulate nerve signal propagation • controls the uptake of neurotransmitters • Protect by surrounding and buffering • Speed transmission by forming myelin sheaths

17. Quizz Glial cells have numerous functions. Which one of these is NOT one of its functions. • To produce myelin sheathing • Protect by surrounding and buffering • Summing signals to trigger an action potentials • A and C

18. Think About This • Each cell has a criteria for firing • criteria shift • No one neuron firing is sufficient information, the meaning is in the average rate in a given population.

19. Thinking MachinesPinker, How the Mind Works • How do you get neurons to represent simple logical functions? • By setting the threshold • This requires pre-wiring • But cannot pre-wire for every thing in the world like mouse or justice.

20. Thinking MachinesPinker, How the Mind Works • Instead of one-neuron-one-symbol the brain uses distributed representation • Many categories combined (e.g., crispy, green, edible) sum up to create one value (e.g., celery)

21. Thinking MachinesPinker, How the Mind Works • Turn the network upside down, and you can represent the fuzzy quality of logic where tokens can be more or less good examples of a category. • Here the item tomato only lights up some of the qualities for fruit

22. Thinking MachinesPinker, How the Mind Works • The neuron at the top is removed and the correlations amongst the nodes is preserved. • The everything-connects-to-everything is called auto-associator, and has five features in common with human pattern recognition.

23. Thinking MachinesPinker, How the Mind Works • Five features of Auto-associators • Reconstructive and content addressable memory • Specifying an item in memory automatically lights up a copy or version of that memory anywhere else. If you light one part of the network, if the weights are strong enough, the parts will light up. So you can recognize a word that has ‘mudsplashes’ on it. • Graceful degradation. Do not discard the whole percept because of one faulty piece of information (e.g., PRITN, HELF) • Constraint satisfaction. • Sinned a pin does not make sense. • But send a pen does even though the sounds are very similar. • With logic you have to test each possibility. With auto-associator the context is intrinsic to the network, and the most meaningful evaluation emerges. Ambiguities are allowed: Necker Cube.

24. Thinking MachinesPinker, How the Mind Works • Five features of Auto-associators • Generalizes automatically. • E.g., bottom row is distributed pattern for an animal (parrot). The top row are the features of the category the animal belongs to (feathers, beak, flies). The relationship amongst the features of a category have an intrinsic correlation. 5. Learn from examples, where learning is a change in the weights.

25. White Matter and Grey Matter

26. Cat Raccoon Rabbit Camel Kangaroo Baboon Human Monkey What is the Order of Intelligence? Why?

27. Forebrain

28. Function of Limbic System

29. Hindbrain

30. 0 Lobes of the Cerebral Cortex • Frontal • Reasoning & Planning • Parietal • Touch, Temperature, Pain, & Pressure • Temporal • Auditory & Perceptual processing • Occipital • Visual processing

31. The Cortex“The Bark”

32. Prefrontal Cortex • Recall the order of things • Provides the brakes on impulse control • Damage can produce Tourette’s like symptoms of tic or exclaiming obscenities

33. Story of Phineas Gage: Damage to the Prefrontal cortex Gage was fitful, irreverent, indulging at times in the grossest profanity (which was not previously his custom), manifesting but little deference for his fellows, impatient of restraint or advice when it conflicts with his desires, at times pertinaciously obstinate, yet capricious and vacillating, devising many plans of future operations, which are no sooner arranged than they are abandoned in turn for others appearing more feasible. A child in his intellectual capacity and manifestations, he has the animal passions of a strong man. Previous to his injury, although untrained in the schools, he possessed a well-balanced mind, and was looked upon by those who knew him as a shrewd, smart businessman, very energetic and persistent in executing all his plans of operation. In this regard his mind was radically changed, so decidedly that his friends and acquaintances said he was 'no longer Gage.’

34. Testing the Prefrontal cortex: The Wisconsin Card Sorting task • The patient is told to sort the cards, but they are not told how to sort. • But they are told if they matched the cards correctly. • They must use their memory for the order of things to figure out the rules of the sorting. • It took an entire manual to score the test, nowadays it is done on the computer.

36. Primary Somatosensory and Motorsensory Cortex